Previous studies have shown utility of isoniazid for ameliorating cerebellar postural tremor in patients with multiple sclerosis. Current studies are aimed at identifying whether patients with action tremors of other types are also benefitted. A double-blind placebo-controlled, cross-over trial is in progress. Twenty patients have now been studied. Isoniazid does appear to help some of these cases, but we do not have enough experience yet to predict the response.